Make Yes/No, Multi, Slider, and Bind items allow enter key to change
value without mouse over item. Add support for left and right arrow keys
and joystick button 1-4 to Yes/No, Multi, and Slider and many item
specific 'ownerdraw' key handlers.
Listbox still requires mouse hover and Team Arena main menu requires
mouse hover to get anywhere...
Enabling K_JOY1-4 to select in default key handler also caused additional
mouse button (K_AUX1-16) to select, which is done in q3_ui as well. Both
handle K_AUX equally badly (not treated as a mouse button and not handled
by item specific key handlers), so it's probably fine.
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